Final: Lecture 22 Flashcards

0
Q

Musculature of the GI tract:

A
  • Skeletal muscle at either end, including upper esophagus

* Smooth muscle throughout most of the length

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1
Q

Epithelium of the GI tract:

A
  • Stratified squamous at either end for protection and resisting friction
  • Simple columnar most of the length
  • With glands along most of the length of tract
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2
Q

The GI tract possesses an intrinsic rhythmicity, mostly due to the presence of an _________.

A
  • Enteric nervous system, exists independently of external influences including ANS
  • Also receives input from sympathetic and para nervous system
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3
Q

The three peptide neurotransmitters are:

A
  • Bombesin
  • Motilin
  • Vasoactive intestinal peptide
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4
Q

Unicellular endocrine cells

A
  • Secrete neuropeptides

* Derived from endoderm unlike intrinsic nerve fibers, which are derived from neural crest

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5
Q

Lymphoid tissue

A
  • Most of the immune system is found in the gut*

* MALT (mucosal associated lymphoid tissue) referred to as GALT in the gut tube

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6
Q

GI Protective mechanisms

A
  • Production of large amounts of mucous, assists in lubrication and friction reduction
  • Rapid turnover of epithelial cells in harsh environment such as stomach and small intestine (if breaks down you get ulcers)
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7
Q

3 embryonic tissues interact in the development of teeth:

A
  • Ectoderm forms the enamel organ: consists of cells committed to formation of enamel, formed from ectoderm under influence of mesoderm and neural crest
  • Neural crest and meso give rise to dental papilla: forms dentin, cementum, and pulp as well as surrounding CT and periodontal pulp
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8
Q

Dentin

A
  • Similar to bone but harder
  • 20% of matrix organic (compared to 35% in bone) and composed mostly of collagen type I (second hardest substance in body)
  • Synthesized by odontoblasts: line pulp cavity as a single layer of cells, apical processes occupy dentinal tubes
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9
Q

Cementum

A
  • Similar to bone

* Covers dentin of the roots of the tooth

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10
Q

Enamel

A
  • Covers crown of tooth (>97% inorganic)
  • Hardest substance in body
  • Synthesized by ameloblasts: secreting apical domains = Tomes’ processes
  • Specific organic components, rather than collagen, are unique to enamel and are removed after calcification: amelogenins, enamelins
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11
Q

Periodontal ligament

A
  • Highly metabolically active tissue
  • Binds cementum to bony socket
  • Allows limited movement
  • Absorbs pressures of mastication and prevents this pressure from damaging alveolar bone
  • Affected by diseases such as diabetes and scurvy
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12
Q

Tongue

A
  • Mass of skeletal muscle covered by stratified suqamous epithelium and elevated projections called papillae
  • Filiform papillae: lack taste buds
  • Fungiform papillae
  • Foliate papillae: rudimentary in adult humans
  • Circumvallate papillae
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13
Q

Taste buds

A
  • Contain two types of cells derived from a single stem cell
  • Sustentacular cells: support cells
  • Taste cells: possess apical microvilli with taste receptors, basal part of cell releases neurotransmitters
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14
Q

Von Ebner’s glands

A

•Serous glands whose ducts empty into the moats at the bases of the circumvallate papillae

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15
Q

Taste Sensation

A
  • Except for bitter taste, sensations utilize varios signal transduction pathways tha result in depolarization of taste cells
  • Salt and sour utilize ionic transport as signal transduction mechanism
  • Sour involved H+ blockage of K+ ion channels to cause depolarization
16
Q

Bitter taste involves a ________ state similar to retinal cell signal transduction.

A
  • Hypopolarized
  • Involves gustucin (homologue of retinal transducin)
  • Involves activation of G subunit, decrease in cGMP, and closure of Na channels and hypopolarization of taste cells
17
Q

Sweet taste involves a ________ state.

A
  • Hyperpolarized
  • Involves activation of G subunit, elevation of cAMP levels and closure of K+ channels and depolarization of the taste cells
18
Q

Layers of Digestive Tube

A

•Mucosa, Submucosa, Muscularis externa, Serosa

19
Q

Mucosa (innermost)

A
  • Stratified squamous transitioning to simple columnar
  • Lamina propria: Loose CT ass. with epithelium
  • Muscularis mucosa
20
Q

Submucosa

A
  • Dense, irregular CT
  • Vascularized
  • Contains a nerve plexus: Meissner’s plexus
21
Q

Muscularis externa

A
  • Inner circular layer of smooth muscle, outer longitudinal layer
  • Myenteric (Auerbach’s) nerve plexus lies between the two layers
  • Functions: regulates the size of lumen and rhythmic movement of the GI tract
22
Q

Serosa (adventitia) composed of _________ CT.

A

•Dense irregular

23
Q

Esophagus

A

•Functions: digestion (initiated in the mouth), addition of mucous to food bolus

•Muscularis externa: undergoes transition from skeletal muscle in upper third to mix of skeletal and smooth in middle third
to smooth only in lower third

•Stratified squamous until it reaches stomach, then simple columnar

24
Q

Stomach

A
  • Caria: contains mostly mucous glands
  • Fundus: contains gastric glands, long tubular glands extending down to the muscularis mucosae, composed of mucous neck cells, parietal cells, chief cells, stem cells, and enteroendocrine cells
  • Body: contains gastric glands
  • Pylorus: contains mucous glands and hormone-secreting enteroendocrine cells
25
Q

Stomach structural specializations:

A
  • Rugae, Esophagogastric sphincter
  • Parietal cell: unique cell of the gastric gland, large pyramidal shape, eosinophilic cell
  • **produces HCL and gastric intrinsic factor*
  • generates H+ ions from carbonic acid similar to osteoclast, prominent intracellular canaliculi lined by microvilli, tubulovesicle pools are part of exocytosis-endocytosis function
26
Q

Chief cells secrete?

A

•Pepsinogen, designed to work at low pH, digest proteins

27
Q

Enteroendocrine cells are small cells with secretory vesicles polarized toward basal surface in proximity to blood vessels and produce ______ and ______.

A
  • Peptide hormones

* Serotonin